TOKYO — Rescuers were searching Monday for a young boy whose parents abandoned him in bear-inhabited woods as a form of punishment.

Police said Yamato Tanooka, 7, has been missing for two days on northern Hokkaido island.

A Hokkaido police spokesperson told NBC News the boy's parents initially said their son became separated from them while looking for wild plants in the woodland.

However, police told NBC News that a family member changed the story the next day to say Tanooka had been left behind as a “form of discipline.” Relatives couldn’t find the boy when they returned moments later, police added.

Police would not say why the boy was being punished or how long he was on his own. Local media reported he was out of sight for just five minutes and that he was disciplined for throwing rocks at cars.

Tanooka's father was asked on Japanese television why the family had changed its story.

"I couldn’t bring myself to say it was to discipline him … and then ask the police to search for him," said the father, whose name has been withheld by officials.

"I want to apologize to my son, also for causing trouble for so many people," he added. "I'm just filled with the feeling hoping that he comes back safely."

More than 100 rescuers deployed Monday to search for the missing boy.

The area is home to brown bears and local television showed pictures of rescuers wearing bear bells, which some claim reduce the chance of surprising the animals.

Arata Yamamoto has been a NBC News producer in Tokyo, Japan, since 1993. He has worked on an array of stories, including the 2004 Asian tsunami, the 2011 tsunami and Fukushima nuclear disaster in Japan, and Haiyan typhoon that struck The Philippines in 2013.